There's be mention made of the fact that OS X Lion Server ships with PostgreSQL as it's standard database rather than MySQL.

Can anyone confirm:

It this specific to server or does OS X Lion "client" ship with it too?

I can see indications in the file system on my Mac that it might be
included but don't know whether they're the result of a previous
aborted Postgres install I did on my machine pre-Lion or just some
form of standardisation of directory structures that stops short of
an actual install.

Is this intended for use as an end user database or is it just supporting functionality within the OS?

"OS X doesn't use a relational database for anything as far as I know". Actually, it makes quite heavy use of SQLite.
–
ThiloJul 29 '11 at 9:55

@Thilo well, but that's a different story, SQLite you know, is far from being a process like PostgreSQL. I believe you know what I mean. OS X doesn't have SQLite server running for its own usage that you could use and create dbs, and users, and host applications into.
–
Martín MarconciniJul 29 '11 at 11:37

1) Yes, it's included in Lion's client factory default from my 2011 macbook air. I found it accidentally, psql -v will gives you postgresql's latest version, which is version 9 at the moment, entering which psql will give you it's path which resides in /usr/bin/psql. I found postgresql's default user which is _postgres, simply change the password to your desired password as you will by entering sudo passwd _postgres.

2) Nope, I didn't think it's for end user database. Even though the psql binary is there, I couldn't found where's the initdb to initialize the database. But, I can't confirm whether it's to support lion's internal system or not, maybe someone can confirm this part?

If you need a working postgresql installation, my suggestion would be installing from source, by using the user _postgres.